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Diagnostic Assessment: Your Intervention Must Have

Diagnostic assessment was the third most effective technique to improve student achievement in an analysis of over 800 education studies by Wisniewski, Zierer, and Hattie. When used effectively to inform instruction, diagnostic assessment can double the speed of student learning (Black and Wiliam, 2009). But why is diagnostic assessment so effective and are there any disadvantages to using this method?

What is a diagnostic assessment?

A diagnostic assessment is a type of assessment or test used to evaluate a student’s strengths, weaknesses, and skills. The results are not used for grading purposes, but used to make adjustments to the direction of a lesson by identifying learners’ key misconceptions. 

Also known as formative assessment, the purpose of this type of assessment is to gather information about students’ understanding in order to make modifications to the learning process. They can be effectively used in every school year and at every stage of the learning process. 

Read more: Formative and summative assessment

Why is diagnostic assessment key to pupil progress?

Diagnostic assessments provide teachers with instant and continuous feedback about what learning has occurred for each pupil in their class. This enables teachers to make informed decisions about how to proceed with the lesson and whether they need to adapt their lesson plan.  

As such, these assessments are essential to improving learner outcomes. They can increase the speed and effectiveness of learning by: 

  • Reducing the time spent teaching information that students already know
  • Directly challenging the most common misconceptions held in a class
  • Identifying students who require a small-group intervention or revision programme

The importance of diagnostic assessment

  • Diagnostic assessments are quick for students to answer which means they can be incorporated frequently into every lesson.
  • It is possible to get responses from every pupil in the class simultaneously
  • Each wrong answer reveals a misconception without requiring further explanations
  • Teachers know which misconceptions need to be challenged
  • Teachers can assess prior knowledge and save time by only teaching the topics required
Number and Place Value Diagnostic Quiz

Number and Place Value Diagnostic Quiz

Gain complete diagnostic insight into your class and inform planning for future lessons

What are common diagnostic assessment tools?

The most appropriate format for a diagnostic tool will vary between subjects and be dependent on the learning that needs to be assessed.  When deciding which tool to use, teachers should consider the three guiding questions of formative assessment and the subsequent questions associated with each one:

Where are we going?

It is important for teachers to consider this question before beginning a lesson or series of lessons and to be clear about the learning goals for their students.  

  • What were the learning objectives for the lesson or this part of the lesson?  
  • What do I expect students to have achieved at this point?  

Where are we now?

Formative assessment can then be used throughout each lesson to effectively measure learners’ understanding against these goals. Asking the question: where are we now?. All formative assessments must incorporate actions to improve learning.  

  • What questions can be asked to know whether the learning objectives have been met?  

Where should we go next?

However, diagnostic assessments are specifically designed to answer this third question. Identifying learners’ misconceptions, allows teachers to make informed decisions about the most appropriate course of action to improve learning. 

  • What misconceptions might students have?
  • How will their answers reveal these misconceptions?  
  • What type of question (e.g. open or closed) will provide answers that I can translate into misconceptions?  

Examples of diagnostic assessments

Multiple-choice questions are usually the most effective form of diagnostic assessment. Each incorrect answer can be chosen to reveal a specific maths misconception and the question can be designed so that students can only answer it correctly if they do not hold a misconception related to that topic. The discrete list of answers makes it quick for the teacher to mark and students can receive instant feedback about their understanding. Students can also complete them in no more than ten seconds, which means that they can be used frequently throughout every lesson without sacrificing valuable learning time. Frequent diagnostic assessments help learners to become more reflective and able to identify which topics require greater revision.

Third Space Learning’s diagnostic assessment, Mission Zero

At Third Space Learning, all pupils sit our interactive, online diagnostic maths test before they start their one to one online maths tutoring programme with us. Our diagnostic assessment informs pupils’ personalised programme of lessons. 

Our diagnostic questions are in multiple choice format. For each question, we’ve created one correct answer and three distractors. Each distractor is based on a specific misconception. This means we’re not only diagnosing where pupils are lacking in knowledge, but also what common misconceptions are holding them back.

However, other examples of diagnostic assessments include:

  • Open-ended questions 
  • Closed questions
  • Hinge questions
  • Practice tests
  • Low-Stakes Quizzes 
  • Short questionnaires
  • Reading assessments
  • Worksheets
  • Multiple Choice Questions

Third Space Learning has created diagnostic questions for numeracy, including fractions and place value, and for students in key stages 3 and 4.  You can download their baseline and diagnostic tests for free using these links:

You can also access advice and shared learning resources for diagnostic assessments and effective questioning here, as well as how we use diagnostic assessment to improve teaching in our one to one online maths tutoring sessions.

Advantages and disadvantages of diagnostic assessment

Diagnostic assessment allows teachers to quickly and accurately assess students’ understanding and get valuable information about the misconceptions that are causing a barrier to learning. When teachers challenge these misconceptions and use students’ answers to make decisions about the next stage of the lesson, learning moves forward faster than it would have in the absence of the diagnostic assessment. This is a huge advantage as lesson time can be used more effectively with teachers focusing on knowledge gaps rather than going over information that the whole class is already secure with.

However, these assessments can be time-consuming to create. Experienced teachers may find it easier to create diagnostic assessments as it requires subject-specific pedagogical knowledge to accurately identify potential misconceptions and write questions that can reveal these.  Schools may need to invest money in teachers’ professional development to fully utilise the impact of diagnostic assessment to ensure teachers have the skills to effectively challenge misconceptions and move learning forward. This can also be mitigated by sharing resources with colleagues and through online professional communities.

What makes a good diagnostic assessment?

When designed effectively, each incorrect answer will reveal a different misconception about the topic being assessed, which makes it easy for teachers to analyse the results and adapt their teacher accordingly. A good diagnostic assessment will allow teachers to confidently make decisions about how to proceed with the next stage of their lesson or how to begin the following lesson. Pupils’ outcomes from these decisions must also be greater than any decision that would have been made in the absence of a diagnostic assessment.  

Common features of effective diagnostic assessments: 

  • Questions are clear and unambiguous (often closed and multiple choice)
  • The focus of the assessment is on one single skill or concept
  • Students’ incorrect answers reveal their misconceptions without the need for further explanation
  • The correct answer cannot be reached if students hold a misconception
  • Students can answer each diagnostic question in less than ten seconds

Diagnostic assessments should support student self-regulation

Incorporating multiple diagnostic assessments into every lesson and providing students with instant feedback about their learning will improve metacognition and their ability to self-regulate.  Referring to incorrect answers as misconceptions will reinforce the message that diagnostic assessments provide valuable learning opportunities and information about students’ knowledge and current understanding. This can include whole class feedback where students have the opportunity to respond to teacher feedback on their work together.

Another easy way to incorporate metacognition into diagnostic assessments is to ask students to rate how confident they are in their answers before revealing the correct answers. While this encourages students to reflect on their answers, it also enables teachers to take advantage of the hypercorrection effect: when a student is confident about an incorrect answer, they are more likely to get the answer right in subsequent tests. 

Providing a confidence rating does not need to add very much time to complete a diagnostic assessment; students can just write down a number between 1 and 5 to represent how confident they are or indicate which emoji is most representative of their confidence.

For multiple-choice questions, teachers could provide students with a copy of the image below to evaluate how confident they are in one or more of the proposed answers.

diagnostic assessment for student
diagnostic assessment quiz for student

Image 1: the student is confident that the correct answer is A.

Image 2: the student believes the answer is either A or B but doesn’t know which one is more likely to be correct.

Image 3: the student is quite confident that the correct answer is D but also thinks A is a possibility.

How can I use diagnostic assessment to inform ongoing teaching?

To improve learning, teaching must be adaptive and tailored to students’ needs. Diagnostic assessment provides teachers with the tools to do this quickly and effectively when three key practices are followed (Andrade & Heritage, 2017).

  1. Integrate the assessments into the process of teaching and learning

Before starting a lesson, a diagnostic test can be used as a pre-test to assess prior learning. Further assessments throughout the lesson and at the end of the lesson can be used to assess the effectiveness of the teaching strategies and instruction.   

When diagnostic questions are used throughout every lesson, they must be quick to execute and not create a distraction from the learning activities.  Popular approaches include:

  • Presenting multiple choice questions on a PowerPoint presentation 
  • Giving students an entry ticket or worksheet to answer the question on
  • Asking students to write their answers on mini-whiteboards
  • Numbering multiple choice questions from 1 to 4 so that students can hold up the number of fingers that corresponds to their answer
  1. Use students’ responses to move learning forward

The purpose of a diagnostic assessment is to enable teachers to make an informed decision about the best course of action for the next stage of learning.  It is only possible to do this effectively if:

  • The diagnostic assessment is designed to diagnose students’ misconceptions effectively
  • The classroom culture supports students to complete the diagnostic assessments honestly
  • Teachers have sufficient training to move learning forward once they have identified their students’ misconceptions
  1. Design effective diagnostic assessments

The assessment method a teacher uses should be tailored to each class. For example, students who are nervous about giving an incorrect answer, being allowed to give their answer non-verbally and not written down can give them the confidence to attempt each question. Asking students to hold up the number of fingers (1, 2, 3, or 4) that corresponds to their multiple-choice answer is an effective way of helping students who lack confidence.  

Classroom culture must also support students to answer diagnostic questions honestly and not opt out. Teachers should aim to create a shared mindset that incorrect answers represent a learning opportunity. This mindset can be encouraged by teachers referring to incorrect answers as misconceptions and sharing the purpose of diagnostic assessments with their students. 

For support in creating a diagnostic assessment, sharing resources between colleagues, either informally or through online communities. Third Space Learning is a leading provider of free diagnostic questions to support teachers delivering the national curriculum for mathematics.  They have created a bank of multiple-choice diagnostic assessments that can be downloaded here: 

Support For Teachers With Diagnostic Assessments

Schools should provide support for teachers to effectively use diagnostic assessments to improve learning.  

  • Educating teachers about the importance of using diagnostic assessment to move learning forwards
  • Providing teachers with the pedagogical knowledge required to create effective diagnostic questions
  • Increasing access to teaching resources and a range of strategies to challenge students’ misconceptions 

Diagnostic assessments FAQs

Are diagnostic assessments a type of formative or summative assessment?

Diagnostic assessments are a type of formative assessment. They are designed to improve learning rather than just provide an evaluation of learning.

What is the purpose of diagnostic assessments?

The purpose of a diagnostic assessment is to improve learning by identifying students’ misconceptions and making these explicit to the teacher.

How long should a diagnostic assessment last?

Each question within a diagnostic assessment should take no more than ten seconds for a student to complete.

When should teachers conduct diagnostic assessments?

Diagnostic assessments should be conducted throughout every lesson, at each stage of the learning process, and whenever a decision needs to be made by the teacher about what should happen next in the lesson.


Andrade, H.L. and Heritage, M., 2017. Using formative assessment to enhance learning, achievement, and academic self-regulation. Routledge.

Wisniewski, B., Zierer, K. and Hattie, J., 2020. The power of feedback revisited: A meta-analysis of educational feedback research. Frontiers in Psychology, 10, p.3087.

Do you have student who need extra support in maths?
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Since 2013 we’ve helped over 150,000 primary and secondary school pupils become more confident, able mathematicians. Learn more or request a personalised quote for your school to speak to us about your school’s needs and how we can help.

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Zoe Benjamin
Zoe Benjamin
Zoe is a secondary maths teacher with responsibility for whole-school teaching and learning. She has previously been Head of Maths in a secondary school and international school. She now enjoys studying the science of learning and writing blog posts for Third Space Learning.
Number and Place Value Diagnostic Quiz

Number and Place Value Diagnostic Quiz

Gain complete diagnostic insight into your class and inform planning for future lessons

Download FREE Now!

Number and Place Value Diagnostic Quiz

Downloadable resource

Gain complete diagnostic insight into your class and inform planning for future lessons

Download FREE Now!

FREE Guide to Hands on Manipulatives

Download our free guide to manipulatives that you can use in the maths classroom.

Includes 15 of the best concrete resources every KS1 and KS2 classroom should have.

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